SGDK VRAM (Video Memory) management unit. More...

Classes
struct	VRAMRegion
	VRAM region structure. More...
Functions
void	VRAM_createRegion (VRAMRegion *region, u16 startIndex, u16 size)
	Initialize a new VRAM region structure.
void	VRAM_releaseRegion (VRAMRegion *region)
	Release the VRAM region structure.
void	VRAM_clearRegion (VRAMRegion *region)
	Release all allocations from specified VRAM region.
u16	VRAM_getFree (VRAMRegion *region)
	Return the number of free tile remaining in the specified VRAM region.
u16	VRAM_getAllocated (VRAMRegion *region)
	Return the number of allocated tile in the specified VRAM region.
u16	VRAM_getLargestFreeBlock (VRAMRegion *region)
	Return the largest free block index in the specified VRAM region.
s16	VRAM_alloc (VRAMRegion *region, u16 size)
	Try to allocate the specified number of tile in the given VRAM region and return its index.
void	VRAM_free (VRAMRegion *region, u16 index)
	Release the previously allocated VRAM block at specified index in the given VRAM region.

Detailed Description

SGDK VRAM (Video Memory) management unit.

Author:: Stephane Dallongeville

Date:: 11/2015

Video Memory management unit.
It offerts methods to manage dynamic VRAM allocation for tile data.
Tile data should always be located before tilemap in VRAM (0000-XXXX = tile data, XXXX-FFFF = tilemaps).

 VRAMRegion structure define a VRAM region where we want to use dynamic allocation.
 'vram' field is a buffer representing the VRAM region usage. For each entry:
  b14-b0 = size of the bloc (in tile)
  b15    = 1:used, 0:free

  address           value

                  +-------------------+
  free = 0        | cacheSize  (free) |
                  |                   |
                  |                   |
  cacheSize - 1   |                   |
                  +-------------------+
  cacheSize       | 0                 |
                  +-------------------+

  1. Before allocation (with cacheSize = 1000)

                  +-------------------+
  free = 0        | 1000       (free) |
                  |                   |
                  |                   |
  999             |                   |
                  +-------------------+
  1000            | 0                 |
                  +-------------------+

  cache = ???
  free = cache            *free = cacheSize
  end = cache+cacheSize   *end = 0

  2. After allocation of 32 tiles

                  +------------------------+
  0               | 32              (used) |
  free = 32       | 968             (free) |
                  |                        |
                  |                        |
  999             |                        |
                  +------------------------+
  1000            | 0                      |
                  +------------------------+

  cache = ???
  free = cache + 32       *free = cacheSize - 32

  3. After allocation of 128 tiles

                  +------------------------+
  0               | 32              (used) |
  32              | 128             (used) |
  free = 32+128   | 840             (free) |
                  |                        |
                  |                        |
  999             |                        |
                  +------------------------+
  1000            | 0                      |
                  +------------------------+

  4. After allocation of 64, 500, 100 tiles

                  +------------------------+
  0               | 32              (used) |
  32              | 128             (used) |
  160             | 64              (used) |
  224             | 500             (used) |
  724             | 100             (used) |
  free = 824      | 176             (free) |
                  |                        |
                  |                        |
  999             |                        |
                  +------------------------+
  1000            | 0                      |
                  +------------------------+

  5. After release of allocation #3 (64 tiles)

                  +------------------------+
  0               | 32              (used) |
  32              | 128             (used) |
  160             | 64              (free) |
  224             | 500             (used) |
  724             | 100             (used) |
  free = 824      | 176             (free) |
                  |                        |
                  |                        |
  999             |                        |
                  +------------------------+
  1000            | 0                      |
                  +------------------------+

  6. After release of allocation #4 (500 tiles)

                  +------------------------+
  0               | 32              (used) |
  32              | 128             (used) |
  160             | 64              (free) |
  224             | 500             (free) |
  724             | 100             (used) |
  free = 824      | 176             (free) |
                  |                        |
                  |                        |
  999             |                        |
                  +------------------------+
  1000            | 0                      |
                  +------------------------+

  7. After allocation of 400 tiles

                  +------------------------+
  0               | 32              (used) |
  32              | 128             (used) |
  160             | 400             (used) |
  560             | 164             (free) |
  724             | 100             (used) |
  free = 824      | 176             (free) |
                  |                        |
                  |                        |
  999             |                        |
                  +------------------------+
  1000            | 0                      |
                  +------------------------+
 *

Function Documentation

s16 VRAM_alloc	(	VRAMRegion *	region,
		u16	size
	)

Try to allocate the specified number of tile in the given VRAM region and return its index.

Parameters:

region	VRAM region
size	Number of tile we want to allocate in VRAM (need to be > 0).

Returns:: the index in VRAM where we allocated the bloc of tile.
-1 if there is no enough available VRAM in the region.

See also:: VRAM_free(..)

void VRAM_clearRegion ( VRAMRegion * region )

Release all allocations from specified VRAM region.

Parameters:

region VRAM region we want to clear.

void VRAM_createRegion	(	VRAMRegion *	region,
		u16	startIndex,
		u16	size
	)

Initialize a new VRAM region structure.

Parameters:

region	Region to initialize.
startIndex	Tile start index in VRAM.
size	Size in tile of the region.

Set parameters and allocate memory for the VRAM region structure.

See also:: VRAM_releaseRegion(..)

void VRAM_free	(	VRAMRegion *	region,
		u16	index
	)

Release the previously allocated VRAM block at specified index in the given VRAM region.

Parameters:

region	VRAM region
index	The index of the VRAM block we want to release

See also:: VRAM_alloc(..)

u16 VRAM_getAllocated ( VRAMRegion * region )

Return the number of allocated tile in the specified VRAM region.

Parameters:

region VRAM region

Returns:: the number of allocated tile in the specified VRAM region.

u16 VRAM_getFree ( VRAMRegion * region )

Return the number of free tile remaining in the specified VRAM region.

Parameters:

region VRAM region

Returns:: the number of free tile in the specified VRAM region

u16 VRAM_getLargestFreeBlock ( VRAMRegion * region )

Return the largest free block index in the specified VRAM region.

Parameters:

region VRAM region

Returns:: the largest free block index in the specified VRAM region.

void VRAM_releaseRegion ( VRAMRegion * region )

Release the VRAM region structure.

Parameters:

region VRAMRegion we want to release.

Release memory used by the VRAM region structure.

See also:: VRAM_createRegion(..)

Classes

Functions

Detailed Description

Function Documentation